The present invention relates generally to a collision warning system and, more particularly, to a method and apparatus for providing a real-time, dynamic display of any terrain hazards so as to prevent Controlled Flight Into Terrain (CFIT). Controlled flight into terrain continues to plague air travel as one of the leading causes of fatal aircraft crashes.
The majority of aircraft are equipped with an inertial guidance system which can calculate the position, velocity, and altitude of an aircraft at any interval after take off for the purpose of directing its future course. Although the system is self-contained and can generate navigational data based on initial time, position, orientation, etc., without the aid of external information, the system is subject to a certain amount of drift.
Aircraft altitude is also measured by a pressure altimeter or a baro-inertial means which provide altitude relative to sea level. Altitude relative to the ground is measured by a radio altimeter which is commonly a low powered radar which measures the vertical distance between the aircraft and the ground. Radio altimeters are an essential part of many avionics systems and are widely used over mountainous regions to indicate terrain clearance. However, the altitude clearance provided is for the aircraft's present position only, and one cannot predict future obstacles.
Also known are laser altimeters in which a laser beam modulated by radio frequencies is directed downward and reflected from the terrain. The reflection is gathered by a telescope system, sensed with a photomultiplier, and phase compared with the original signal.
For the past twenty years, the standard system for alerting the flight crew of an aircraft of an impending collision with terrain has been the Ground Proximity Warning System (GPWS) which warns of potentially dangerous situations where a collision with the terrain may occur. The system relies on measuring the clearance between the terrain immediately below the aircraft and operates by examining the rate of aircraft descent, as measured by a barometric altimeter, the aircraft configuration, and the aircraft's ground clearance to generate a warning if a dangerous flight profile is detected. The GPWS uses basic aircraft data that has no direct knowledge of the real terrain in the vicinity of the aircraft. This system is generally adequate for use in regions having an essentially flat or gently rolling/sloping terrain, however, provides no warning of obstacles in front of the aircraft, such as a mountain range or man-made obstacles (e.g., towers and the like). Because the GPWS operates without knowledge of the real terrain in the vicinity of the aircraft, the result is often a false warning in conditions that are not a real threat, or reduced warning times for real terrain threats. As a result of false alarms, flight crews typically develop an apathy for or mistrust of the warnings. Such apathy or mistrust may lead the crew to ignore a warning or respond less quickly in a real warning situation. While the GPWS systems offer some protection, the number of CFIT accidents is still unacceptably high as a result of the inherent limitations in the GPWS.
The technology is now available to provide an improved method of alerting a flight crew of potential CFIT conditions. This technology includes: (1) accurate aircraft present position information, (2) terrain data and suitable storage means, and (3) computer processing resources. The improved alerting system is referred to as a Ground Collision Avoidance System (GCAS). It utilizes aircraft present position information, aircraft state information, and a digital terrain database to determine the flight path of the aircraft relative to the surrounding terrain. One such system is described by Brame in U.S. Pat. No. 4,224,669, herein incorporated by reference in its entirety.
While the advent of advanced technology aircraft and flightdeck automation may reduce the number of functions a flight crew is actively or directly involved in, the crew's responsibility for correct and timely performance of those activities is not reduced. Where advanced automation facilitates a reduction in crew size, the crew's oversight of cockpit activities may become more difficult as many concurrent activities are performed and monitored by a fewer number of people.
Flight crew inactivity, fatigue, or complacency is one potential side effect of flightdeck automation When automation functions reliably, as it does most of the time, it may induce pilots to be less alert in monitoring aircraft behavior and less prepared to take immediate action when needed.
Another problem with flight deck design is that it may lack a human-centered design philosophy that addresses the capabilities and limitations of humans, and the proper role and function of the human in piloting advanced technology aircraft.
Aircraft monitoring may be necessary for long periods of time and the crew may be required to integrate information spread over several parts of the interface. In some cases, crew workload may be high at certain times and low at others, possibly resulting in periods of excessive workload followed by periods of boredom. The combination of large amounts of information and poor formatting or integration may serve to increase crew workload. It would, therefore, be desirable to provide integration of terrain and other data onto a single display.
It is, therefore, an object of the present invention to provide a terrain awareness display that uses a format that provides a pilot or flight crew with complete situational awareness of potential terrain hazards to the aircraft. The information is formatted to provide an interface that provides the data conveniently, simply, and intuitively in a format that is easily assimilated and interpreted by a human operator.
Another object of the present invention is to provide a terrain awareness display format that integrates horizontal data and flight path profile data onto a single display, but which at the same time is not so abstracted or simplified as to compromise the usefulness of the data in supporting effective flight crew decision making.
Another object of the present invention is to provide a display that provides a visual representation of an aircraft's position relative to terrain and obstacles.
Another object of the present invention is to provide a terrain warning system, whereby the number of false warnings are reduced, and whereby the validity of the warning can immediately and easily be verified.
Yet another object of the invention is to provide a display format further integrating information to provide a flight crew with additional situational awareness concerning other potential hazards, such as other aircraft, weather, and the like.